The invention relates to a device for carrying out a distraction or a compression of vertebral bodies during in particular minimally invasive spinal surgery, said device comprising a first and a second extension part, which parts are in particular sleeve-shaped, at least in portions, each part having a longitudinal direction and each of which parts can be secured on a bone anchor in a detachable but rigid and rotationally fixed manner, the bone anchors in each case being intended to be inserted or being already inserted into one of the vertebral bodies to be treated.
In modern spinal surgery, in particular in minimally invasive spinal surgery where sleeve-shaped extension parts of the bone anchors, referred to as extenders, are used, the problem is often that usually adjacent vertebral bodies have to be moved away from one another (distraction) or moved towards one another (compression). The new position can then be fixed by means of osteosynthesis devices, using correction rods. There are instruments for this purpose in the prior art which are sometimes designed in a complex manner and which connect the two extension parts, which parts are rigidly connected to the bone anchors inserted into the vertebral bodies, so as to be adjustable relative to one another. The known devices are complex to produce and complicated to use.
US 2014/0039557 A1 discloses a device of the type mentioned at the outset. In this device, one of the sleeve-shaped extension parts is provided with a bearing part that can be moved in the longitudinal direction and with which the other bearing sleeve-shaped extension part can be brought into contact in order to form a bearing point. The movable bearing part can be made larger by clipping on an attachment part.
US 2014/0277151 A1 also discloses a device of the type mentioned at the outset, comprising a cup-shaped bearing part which can be placed onto one of the sleeve-shaped extension parts and can optionally be moved relative to the sleeve-shaped extension part in the longitudinal direction, which bearing part comprises U-shaped or wing-shaped attachments or arms that extend outwards in the transverse direction and with which the other sleeve-shaped extension part can be brought into contact in order to form a pivot bearing point. In order to adapt the different transverse spacings of the sleeve-shaped extension parts, different bearing parts having different transverse extents are used, or one bearing part is used, one arm of which is designed so as to be length-adjustable in the transverse direction, it being possible for a rack-like locking mechanism to be used.
Proceeding herefrom, the object of the present invention is that of providing a device of the type mentioned at the outset which is less complex in design than known devices, is easy to use and can be economically produced.